Radiological image conversion panel, method of manufacturing the same, and radiological image detection apparatus

ABSTRACT

A radiological image conversion panel 2 is provided with a phosphor 18 containing a fluorescent material that emits fluorescence by radiation exposure, in which the phosphor includes, a columnar section 34 formed by a group of columnar crystals which are obtained through columnar growth of crystals of the fluorescent material, and a non-columnar section 36, the columnar section and the non-columnar section are integrally formed to overlap in a crystal growth direction of the columnar crystals, and a thickness of the non-columnar section along the crystal growth direction is non-uniform in a region of at least a part of the non-columnar section.

CROSS REFERENCE TO RELATED APPLICATION

This is a Continuation application of U.S. application Ser. No.13/927,529, filed Jun. 26, 2013 which is a continuation of InternationalApplication No. PCT/JP2011/062403 filed on May 30, 2011, and claimspriority from Japanese Patent Application No. 2010-291390, filed on Dec.27, 2010, the entire disclosures of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a radiological image conversion panel,a manufacturing method of the radiological image conversion panel and aradiological image detection apparatus provided with the radiologicalimage conversion panel.

BACKGROUND ART

A radiological image detection apparatus using a Flat Panel Detector(FPD) that detects a radiological image to generate digital image datahas recently been used practically. The radiological image detectionapparatus may immediately confirm an image, as compared to aconventional imaging plate, and thus has been rapidly distributed. Thereare various types of radiological image detection apparatus, and as oneof them, an indirect conversion type of the device is known.

The indirect conversion type of radiological image detection apparatusis provided with a radiological image conversion panel and a sensorpanel having two-dimensionally arranged photoelectric conversionelements, in which the radiological image conversion panel has ascintillator formed of a fluorescent material that emits fluorescencethrough radiation exposure, such as CsI or GOS(Gd₂O₂S). Typically, theradiological image conversion panel and the sensor panel are bonded sothat the scintillator is in close contact with the two-dimensionalarrangement of the photoelectric conversion elements. Radiation passingthrough the subject is first converted into light by the scintillator ofthe radiological image conversion panel, and the fluorescence of thescintillator is photoelectrically converted by a group of thephotoelectric conversion elements of the sensor panel to generate anelectrical signal (digital image data).

As for the indirect conversion type of the radiological image detectionapparatus, there has been suggested a radiological image detectionapparatus of a so-called surface reading type (ISS: Irradiation SideSampling) where radiation is allowed to be incident from the sensorpanel side (for example, see Patent Literatures 1 and 2). According tothe radiological image detection apparatus, the amount of fluorescenceemitted from the scintillator in the vicinity of the sensor panel isincreased, thereby improving the sensitivity. This may reduce theexposure amount required for detecting a radiological image, therebyreducing the exposure dose of the subject.

Also, there is known a technology of forming a scintillator by a groupof columnar crystals through a vapor deposition method so as to improvethe sensitivity, in which the columnar crystals are obtained throughcolumnar growth of crystals of a fluorescent material such as CsI on asupport (for example, see Patent Literature 3). The columnar crystalsformed by the vapor deposition method do not include impurities such asa binding agent, and also has a light guide effect of guiding thefluorescence emitted therefrom in the growth direction of the crystals,thereby suppressing the diffusion of the fluorescence. Accordingly, theimprovement in the sensitivity of a radiological image detectionapparatus and the sharpness of an image may be achieved.

Further, in order to improve the characteristics of a radiological imageconversion panel provided with a scintillator including a group ofcolumnar crystals, various suggestions have been made. For example, inthe radiological image conversion panel described in Patent Literature3, a non-columnar section including a group of spherical crystals of afluorescent material is formed at the support side of the scintillator,and thereon, a columnar section including a group of columnar crystalsis formed. Since the non-columnar section is interposed between thesupport and the columnar section, the improvement in the adhesion of thescintillator with the support is achieved. Also, by the light reflectionin the non-columnar section, the improvement of use efficiency offluorescence, and thereby the improvement of the sensitivity may beachieved.

CITATION LIST Patent Literature

Patent Literature 1: JP-B-3333278

Patent Literature 2: JP-A-2001-330677

Patent Literature 3: JP-A-2005-69991

SUMMARY OF INVENTION Technical Problem

From the viewpoint of light reflection in a non-columnar section,crystals constituting the non-columnar section may preferably have asmall diameter cross-section, and a spherical shape. However, many ofthe crystals constituting the non-columnar section may aggregate withneighboring crystals, so as to form indeterminate aggregates.Accordingly, many of the crystals that constitute the non-columnarsection (or include a non-crystalline part) may be partially fused toeach other, not only in the thickness direction, but also in thein-plane direction. Each of columnar crystals constituting a columnarsection grows with respect to a nucleus of a part of such anindeterminate aggregate. In such a case, columnar crystals with arelatively smaller diameter grow at the initial growth. Then, as thegrowth proceeds, a plurality of neighboring columnar crystals aggregatewith each other, thereby forming one columnar crystal with a largediameter. The junction portion of the columnar section with thenon-columnar section has bristled columnar crystals with a relativelysmall diameter which causes many gaps therebetween, and is very weakagainst a stress acted by shock, especially, a shear force.

Especially, the scintillator described in Patent Literature 3 is acumulative phosphor, and a computed radiography (CR) cassette as oneexample of a radiological image detection apparatus using such ascintillator is relatively light. However, as one example of aradiological image detection apparatus using an FPD, a DigitalRadiography (DR) cassette is generally mounted with various electroniccomponents such as a TFT substrate or a driving circuit, and thus isrelatively heavy, and its drop shock is higher than the CR cassette.Accordingly, the protection of the scintillator becomes important.

The present invention has been made in consideration of the abovedescribed problems and its object is to improve the strength of aradiological image conversion panel.

Solution to Problem

(1) It is a radiological image conversion panel provided with a phosphorcontaining a fluorescent material that emits fluorescence by radiationexposure, in which the phosphor comprises, a columnar section formed bya group of columnar crystals which are obtained through columnar growthof crystals of a fluorescent material, and a non-columnar section, thecolumnar section and the non-columnar section are integrally formed tooverlap in a crystal growth direction of the columnar crystals, and athickness of the non-columnar section along the crystal growth directionis non-uniform in a region of at least a part of the non-columnarsection.

(2) It is a method of manufacturing the radiological image conversionpanel of (1), in which the non-columnar section and the columnar sectionare formed in this order on a support by depositing crystals of thefluorescent material on the support by a vapor deposition method, inwhich when the non-columnar section is formed, the crystals of thefluorescent material are deposited on the support by varying a degree ofvacuum.

(3) It is a radiological image detection apparatus provided with theradiological image conversion panel of (1), and a sensor panel whichdetects fluorescence generated from the radiological image conversionpanel and converts the fluorescence into an electrical signal.

Advantageous Effects of Invention

According to the present invention, in a region of at least a part ofthe non-columnar section, the thickness is non-uniform, and the junctionportion between the columnar section and the non-columnar section isuneven in the plane direction. Accordingly, the resistance againststress such as a shear force may be improved, thereby improving thestrength of the radiological image conversion panel.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view schematically illustrating a configuration of aradiological image detection apparatus according to one exemplaryembodiment of the present invention.

FIG. 2 is a view schematically illustrating a configuration of a sensorpanel of the radiological image detection apparatus of FIG. 1.

FIG. 3 is a view schematically illustrating a configuration of aradiological image conversion panel of the radiological image detectionapparatus of FIG. 1.

FIG. 4 is a view illustrating a IV-IV cross section of a phosphor of theradiological image conversion panel of FIG. 3.

FIG. 5 is a view illustrating a V-V cross section of a phosphor of theradiological image conversion panel of FIG. 3.

FIG. 6 is a view schematically illustrating a modified example of theradiological image conversion panel of FIG. 3.

FIG. 7 is a view schematically illustrating a configuration of aradiological image detection apparatus according to another exemplaryembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates a configuration of a radiological image detectionapparatus according to one exemplary embodiment of the presentinvention, and FIG. 2 illustrates a configuration of a sensor panel ofthe radiological image detection apparatus of FIG. 1.

A radiological image detection apparatus 1 is provided with aradiological image conversion panel 2 that includes a scintillator 18(phosphor) that emits fluorescence by radiation exposure, and a sensorpanel 3 that includes two dimensional arrangement of photoelectricconversion elements 26 which photoelectrically convert the fluorescenceof the scintillator 18 of the radiological image conversion panel 2.

The radiological image conversion panel 2 includes a support 11 on whichthe scintillator 18 is formed. The radiological image conversion panel 2is configured separately from the sensor panel 3, and is bonded to thesensor panel 3 via a resin layer, in which the resin layer allows thescintillator 18 to be optically coupled to the photoelectric conversionelements 26 while the surface of the scintillator 18 at the oppositeside to the support 11 faces the two-dimensional arrangement of thephotoelectric conversion elements 26 of the sensor panel 3.

In the present exemplary embodiment, radiation is irradiated from thesensor panel 3 side, transmitted through the sensor panel 3, andincident on the scintillator 18. The scintillator 18 on which theradiation is incident generates fluorescence, and the generatedfluorescence is photoelectrically converted by the photoelectricconversion elements 26 of the sensor panel 3. In the radiological imagedetection apparatus 1 as configured above, the radiation entrance sideof the scintillator 18 which generates a lot of fluorescence is providedadjacent to the photoelectric conversion elements 26, thereby improvingthe sensitivity.

The sensor panel 3 has a TFT substrate 16 that includes switchingelements 28 formed by Thin Film Transistors (TFTs) on an insulatingsubstrate, and the two-dimensional arrangement of the photoelectricconversion elements 26 is formed on the TFT substrate 16. On the TFTsubstrate 16, a flattening layer 23 configured to cover thephotoelectric conversion elements 26 and flatten the surface of the TFTsubstrate 16 is formed. An adhesive layer 25 configured to bond theradiological image conversion panel 2 to the sensor panel 3 is formed onthe flattening layer 23. The flattening layer 23 and the adhesive layer25 constitute the above described resin layer. Also, as the resin layer,a matching oil or the like made of transparent liquid or gel may beused. The thickness of the resin layer is preferably 50 μm or less, andmore preferably 5 μm to 30 μm from the viewpoints of the sensitivity andthe image sharpness.

Each of the photoelectric conversion elements 26 has a configurationwhere a photoconductive layer 20 that generates electric charges byfluorescence incident from the scintillator 18, and a pair of electrodesprovided at the top and bottom surfaces of the photoconductive layer 20.An electrode 22 provided at the surface of the photoconductive layer 20at the side of the scintillator 18 is a bias electrode that applies abias voltage to the photoconductive layer 20, and an electrode 24provided at the opposite side surface is an electric charge collectingelectrode that collects the electric charges generated from thephotoconductive layer 20.

The switching elements 28 are two-dimensionally arranged on the TFTsubstrate 16 correspondingly to the two-dimensional arrangement of thephotoelectric conversion elements 26, and the electric charge collectingelectrodes 24 of the photoelectric conversion elements 26 are connectedto the corresponding switching elements 28 of the TFT substrate 16. Theelectric charges collected by the electric charge collecting electrodes24 are read out by the switching elements 28.

On the TFT substrate 16, a plurality of gate lines 30 are providedextending in one direction (row direction) to set each of the switchingelements 28 to be ON/OFF, and a plurality of signal lines (data lines)32 are provided extending in a direction (column direction)perpendicular to the gate lines 30 to read out the electric charges viathe switching elements 28 in the ON state. Then, in the periphery of theTFT substrate 16, a connection terminal 38 connected to the gate lines30 and the signal lines 32, respectively, is provided. The connectionterminal 38, as illustrated in FIG. 2, is connected to a circuit board(not illustrated) via a connection circuit 39. The circuit boardincludes a gate line driver as an external circuit, and a circuitprocessing unit.

The switching elements 28 are sequentially placed in the ON state lineby line by the signal supplied via the gate lines 30 from the gate linedriver. Then, the electric charges read out by the switching elements 28placed in the ON state are transmitted as electric charge signals viathe signal lines 32, and input to the signal processing unit.Accordingly, the electric charges are sequentially read out line byline, and converted into electrical signals in the signal processingunit, to generate digital image data.

Hereinafter, the radiological image conversion panel 2 and thescintillator 18 thereof will be described in detail.

FIG. 3 schematically illustrates the configuration of the radiologicalimage conversion panel 2.

The radiological image conversion panel 2 includes the support 11 andthe scintillator 18 formed on the support 11.

As for the support 11, a carbon plate, a carbon fiber reinforced plastic(CFRP), a glass plate, a quartz substrate, a sapphire substrate or ametal sheet selected from iron, tin, chromium, aluminum or the like, maybe used. However, the support is not limited to those described above aslong as it may allow the scintillator 18 to be formed thereon.

As for the fluorescent material constituting the scintillator 18, forexample, CsI:Tl NaI:Tl (thallium-activated sodium iodide), CsI:Na(sodium-activated cesium iodide) or the like may be used. From amongthese, CsI:Tl is preferable since its emission spectrum is suitable forthe maximum value (around 550 nm) of the spectral sensitivity of a-Siphotodiode.

The scintillator 18 is configured to include a columnar section 34provided at the opposite side of the support 11, and a non-columnarsection 36 provided at the support 11 side. The columnar section 34 andthe non-columnar section 36 are continuously formed to be stacked inlayers on the support 11. Although details will be described later, forexample, a vapor deposition method may be used for the formation. Also,although the columnar section 34 and the non-columnar section 36 areformed by the same fluorescent material, the addition amount of anactivator such as Tl may be varied.

The columnar section 34 is formed by a group of columnar crystalsobtained by columnar growth of crystals of the fluorescent material.Also, there is a case where a plurality of neighboring columnar crystalsmay be bonded to each other so as to form one columnar crystal. There isa gap between adjacent columnar crystals, and thus respective columnarcrystals exist independently with each other.

The non-columnar section 36 is formed by a group of spherical crystalsobtained by growing crystals of the fluorescent material in asubstantially spherical shape with a relatively small diameter. Also, inthe non-columnar section 36, a non-crystalline part of the fluorescentmaterial may be included. In the non-columnar section 36 formed by thegroup of the spherical crystals, the crystals (that may partiallyinclude a non-crystalline part) irregularly overlap, and some crystalsmay be fused to each other in the thickness direction or the in-planedirection. Thus, a clear gap between the crystals hardly occurs.

The radiological image conversion panel 2 is bonded to the sensor panel3 while the surface of the scintillator 18 at the opposite side to thesupport 11, that is, the tip of each of the columnar crystals of thecolumnar section 34, faces the two-dimensional arrangement of thephotoelectric conversion elements 26 of the sensor panel 3. Accordingly,at the radiation entrance side of the scintillator 18, the columnarsection 34 including the group of the columnar crystals is disposed.

The fluorescence occurring in each of the columnar crystals of thecolumnar section 34 is suppressed from diffusing since total reflectionwithin the columnar crystal is repeated due to a refractive indexdifference between the columnar crystal and the gap (air) around thecrystal. Then, the fluorescence is guided to the photoelectricconversion element 26 facing the columnar crystal. Accordingly, thesharpness of the image is improved.

The fluorescence which occurs in each of the columnar crystals of thecolumnar section 34 and is toward the opposite side to the sensor panel3, that is, the support 11 side, is reflected toward the sensor panel 3side in the non-columnar section 36. This increases the use efficiencyof the fluorescence, thereby improving the sensitivity.

Also, each of the columnar crystals of the columnar section 34 isrelatively thin at the initial growth, and becomes thicker according tothe crystal growth. At the junction portion 34A of the columnar section34 with the non-columnar section 36, columnar crystals with a smalldiameter are bristled, and many relatively large gaps extend in thedirection of crystal growth, which increases the porosity. At one side,the non-columnar section 36 is formed by spherical crystals with a smalldiameter or aggregates thereof, in which individual gaps are relativelysmall, and are dense as compared to those in the columnar section 34,and thus, the porosity is low. Since the non-columnar section 36 isinterposed between the support 11 and the columnar section 34, theadhesion of the scintillator 18 with the support 11 is the improved.Accordingly, the resistance against stress acted by warping or shock dueto a linear expansion difference between the support 11 and the TFTsubstrate 16 of the sensor panel 3 is improved, and the scintillator 18is suppressed from being peeled off from the support 11.

FIG. 4 is an electron micrograph illustrating a IV-IV cross section ofthe scintillator 18 of FIG. 3.

As can be clearly seen in FIG. 4, in the columnar section 34, thecolumnar crystals show a substantially uniform cross sectional diameterin the crystal growth direction, and also the columnar crystals existindependently with each other with gaps around the columnar crystals.The crystal diameter of the columnar crystals is preferably, 2 μm ormore and 8 μm or less from the viewpoints of a light guide effect, amechanical strength, and a pixel defect prevention. When the crystaldiameter is too small, there is a concern that each of the columnarcrystals lacks the mechanical strength, and thus is damaged by shock orthe like. When the crystal diameter is too large, the number of thecolumnar crystals in each of the photoelectric conversion elements 26 isdecreased. Thus, there is a concern that when a crack occurs in thecrystals, the probability of defect in a corresponding elementincreases.

Here, the crystal diameter refers to a maximum diameter of a crystalobserved from the top surface in the growing direction of the columnarcrystal. In a specific measuring method, the columnar diameter (crystaldiameter) is measured by observation from a plane perpendicular to thefilm thickness direction of the columnar crystals with an SEM (scanningelectron micrograph). Observation is performed with a magnification(about 2,000×) that allows 100 to 200 columnar crystals 20 A to beobserved when the scintillator is viewed from the surface at one shot. Avalue obtained by measuring and taking an average on the maximum valuesof the columnar diameters of columnar crystals obtained for all thecrystals included at the one shot is employed. The columnar diameters(μm) are read to two decimal places, and the average value is determinedby rounding off to one decimal place in accordance with JIS Z 8401.

FIG. 5 is an electron micrograph illustrating a V-V cross section of thescintillator 18 of FIG. 3.

As can be clearly seen in FIG. 5, in the non-columnar section 36, sincethe crystals are irregularly bonded to or overlapped each other, a cleargap between the crystals is not confirmed unlike in the columnar section34. The diameter of the crystals constituting the non-columnar section36 is preferably 0.5 μm or more and 7.0 μm or less from the viewpointsof an adhesion and a light reflection. When the crystal diameter is toosmall, there is a concern that the gap gets closer to 0, therebylowering the light reflection function. When the crystal diameter is toolarge, there is a concern that the flatness is lowered, thereby loweringthe adhesion with the support 11. Also, the shape of the crystalsconstituting the non-columnar section 36 is preferably substantiallyspherical from the viewpoint of the light reflection.

Here, in a case where crystals are bonded to each other, the crystaldiameter is measured as follows. A line connecting concave portions(recesses) occurring between the adjacent crystals is considered as aboundary between the crystals, and the bonded crystals are separated tobe the smallest polygons so that a columnar diameter and a crystaldiameter corresponding to the columnar diameter are measured. Then, theaverage value thereof is determined and is employed in the same manneras the crystal diameter of the columnar section 34.

In the thicknesses of the columnar section 34 and the non-columnarsection 36, when the thickness of the columnar section 34 is set as t1,and the thickness of the non-columnar section 36 is set as t2, (t2/t1)is preferably 0.01 or more and 0.25 or less, and more preferably 0.02 ormore and 0.1 or less. When (t2/t1) is within the above described range,a fluorescence efficiency, a light diffusion prevention and a lightreflection may be placed in a suitable range, thereby improving thesensitivity and the image sharpness.

Also, the thickness t1 of the columnar section 34 depends on the energyof radiation, but is preferably 200 μm or more and 700 μm or less fromthe viewpoints of a sufficient radiation absorption and an imagesharpness in the columnar section 34. When the thickness of the columnarsection 34 is too small, there is a concern that radiation may not besufficiently absorbed, and thus the sensitivity is lowered. When thethickness is too large, there is a concern that the light diffusionoccurs, and thus the image sharpness is lowered even by the light guideeffect of the columnar crystals.

The thickness t2 of the non-columnar section 36 is preferably 5 μm ormore and 125 μm or less from the viewpoints of the adhesion with thesupport 11, and the light reflection. When the thickness of thenon-columnar section 36 is too small, there is a concern that asufficient adhesion with the support 11 may not be obtained. When thethickness is too large, there is a concern that contribution offluorescence in the non-columnar section 36, and diffusion by lightreflection in the non-columnar section 36 are increased, therebylowering the image sharpness.

Further, in the present radiological image conversion panel 2, thethickness distribution of the non-columnar section 36 is non-uniform.Since the columnar section 34 and the non-columnar section 36 arecontinuously formed by crystals of the same fluorescent material, thebonding of the columnar section 34 to the non-columnar section 36 isrelatively stronger as compared to the bonding of the columnar section34 to different materials such as the support 11. However, each of thecolumnar crystals of the columnar section 34 grows with respect to anucleus of a relatively small spherical crystal of the non-columnarsection 36, and is relatively thin at the initial growth, and becomesthicker according to the crystal growth. At the junction portion 34A ofthe columnar section 34 with the non-columnar section 36, columnarcrystals with a small diameter are bristled, and relatively large gapsextend in the direction of crystal growth. Further, although each of thecolumnar crystals becomes thick according to the growth, and a pluralityof neighboring columnar crystals are in contact with each other, thesecrystals are not always bonded (fused) to each other. Accordingly, thereis a concern that the junction portion 34A of the columnar section 34may lack resistance against stress acted by shock or the like.Accordingly, the non-columnar section 36 has non-uniform thicknessdistribution, thereby compensating the stress resistance at the junctionportion 34A.

Due to the non-uniform thickness distribution of the non-columnarsection 36, the junction portion 34A becomes uneven in the planedirection. In each of the columnar crystals growing at the thinthickness region of the non-columnar section 36, the junction portion34A is surrounded by a dense non-columnar section 36 in the neighborhoodthereof. The junction portion 34A of each of the columnar crystalsgrowing at the thick thickness region of the non-columnar section 36 issurrounded by neighboring columnar crystals of which the growth proceedsat the thin thick region of the non-columnar section 36 and the diameterbecomes large. Accordingly, the resistance against stress such as ashear force may be increased, thereby improving the strength.

The thickness of each portion of the non-columnar section 36 ispreferably distributed within the above described range of 5 μm or moreand 125 μm or less from the viewpoints of the adhesion with the support11 and the light reflection. Also, in the present radiological imageconversion panel 2, the non-columnar section 36 has a constantlynon-uniform thickness distribution throughout. However, when thenon-columnar section 36 is divided into a plurality of regions,non-uniformity (difference between the maximum thickness and the minimumthickness, or deviation in the thickness distribution) may be differentin respective regions.

Hereinafter, the method of preparing the above described scintillator 18will be exemplarily descried.

The scintillator 18 is preferably directly formed on the surface of thesupport 11 by a vapor deposition method. In the vapor deposition method,the non-columnar section 36 and the columnar section 34 may be in thisorder sequentially integrally formed. Hereinafter, a case of usingCsI:Tl as the fluorescent material is exemplarily described.

The vapor deposition method may be performed according to a conventionalmethod. Under the environment of degree of vacuum 0.01 Pa to10 Pa,CsI:Tl is heated and vaporized, for example, by means of applyingelectric current to a resistance heating-type crucible, and then thetemperature of the support 11 is adjusted to room temperature (20° C.)to 300° C. so as to deposit CsI:Tl on the support.

When the crystalline phase of CsI:Tl is formed on the support 11 by thevapor deposition method, at the initial stage, spherical crystals with arelatively small diameter or aggregates thereof are formed. Then, byvarying at least one condition of the degree of vacuum, and thetemperature of the support 11, it is possible to form the columnarsection 34 in succession to the formation of the non-columnar section36. That is, after the spherical crystals are deposited to apredetermined thickness, the columnar crystals may be grown byincreasing the degree of vacuum, and/or increasing the temperature ofthe support 11.

Then, in the step of forming the non-columnar section 36, depositionwith variation of the degree of vacuum imparts non-uniform thicknessdistribution to the non-columnar section 36. When the degree of vacuumis varied, the melt state of CsI:Tl is changed. Then, a time is requireduntil the melt state is stabilized. While the melt state is unstable,the deposition may be continuously performed, thereby impartingnon-uniform thickness distribution to the non-columnar section 36.

The scintillator 18 may be efficiently and easily prepared in the manneras described above. Also, according to the preparation method, there isan advantage in that the scintillator with various specifications may besimply prepared in accordance with designs by controlling the degree ofvacuum or the support temperature in the film formation of thescintillator 18.

As described above, in the radiological image conversion panel 2 and theradiological image detection apparatus 1 including the same, thethickness of the non-columnar section 36 of the scintillator 18 isnon-uniform, and the junction portion 34A of the columnar section 34with the non-columnar section 36 is uneven in the plane direction.Accordingly, the resistance against stress such as a shear force may beimproved, thereby improving the strength of the radiological imageconversion panel 2.

Also, although in the above described radiological image detectionapparatus 1, radiation is incident from the sensor panel 3 side, aconfiguration where radiation is incident from the radiological imageconversion panel 2 side may be employed.

Also, although in the above described radiological image detectionapparatus 1, the radiological image conversion panel 2 and the sensorpanel 3 are bonded via the flattening layer 23 and the adhesive layer25, there is no particular limitation in the bonding method between theradiological image conversion panel 2 and the sensor panel 3. Thescintillator 18 of the radiological image conversion panel 2 and thearrangement of the photoelectric conversion elements 26 of the sensorpanel 3 may be optically coupled, or a method of directly bringing thescintillator 18 in close contact with the arrangement of thephotoelectric conversion elements 26 may be employed. In this case, itis not necessary that the surfaces of the two elements are in completelyclose contact with each other. Even though an unevenness exists on thesurface of the scintillator 18, the two elements may be opticallycoupled while disposed in the overlapping state. When the fluorescenceoccurring in the scintillator 18 is incident on the arrangement of thephotoelectric conversion elements 26, the effect of the presentinvention may be achieved.

FIG. 6 illustrates a modified example of the above describedradiological image conversion panel 2.

In the present modified example, although the non-columnar section 36has a non-uniform thickness distribution throughout, a differencebetween the maximum thickness and the minimum thickness in a centralregion 36A is set to be less than a difference between the maximumthickness and the minimum thickness in a peripheral region 36B. That is,the deviation in the thickness distribution in the central region 36A isset to be less than that in the thickness distribution in the peripheralregion 36B.

The scintillator 18 is formed in a size equal to or greater than thetwo-dimensional arrangement of the photoelectric conversion elements 26so as to cover the two-dimensional arrangement of the photoelectricconversion elements 26. Meanwhile, in the two-dimensional arrangement ofthe photoelectric conversion elements 26, elements in a central region(effective imaging region) are generally used for detecting aradiological image because noise may be easily superimposed on elementsin a peripheral region. For this reason, the central region of thescintillator 18, which overlaps the above described effective imagingregion, mainly contributes to the detection of the radiological image.The contribution by the peripheral region excluding the effectiveimaging region is relatively low.

The non-columnar section 36 of the scintillator 18 has a lightreflection function as described above, and the non-uniformity in thethickness of the non-columnar section 36 may induce non-uniformity inlight reflection. Therefore, by reducing the difference between themaximum thickness and the minimum thickness in the central regions 36Aof the non-columnar section 36 overlapping the above described effectiveimaging region, the non-uniformity of light reflection in thecorresponding region may be reduced, thereby lowering the shock on theimage.

Meanwhile, in the peripheral region 36B of the non-columnar section 36,the contribution to the detection of the radiological image isrelatively low as described above, and thus, even though the differencebetween the maximum thickness and the minimum thickness is set to belarge, there is no specific problem. Also, the peripheral region of thescintillator 18 is susceptible to stress caused by warping or shock.Therefore, when the difference between the maximum thickness and theminimum thickness in the peripheral region 36B of the non-columnarsection 36 is set to be large, it is possible to secure the resistanceagainst the stress acted on the junction portion between the columnarsection 34 and the non-columnar section 36.

Further, the thickness distribution in the central region 36A of thenon-columnar section 36 may be uniform, which may uniformize the lightreflection in the central region 34A, thereby further reducing the shockon the detected image. Also, the uniform thickness distributionindicates that the difference between that the maximum thickness and theminimum thickness is less than 5 μm.

The scintillator 18 which has a small deviation in the thicknessdistribution or a uniform thickness distribution in the central region36A of the non-columnar section 36 may be prepared by depositing thecrystals of CsI:Tl with variation of the degree of vacuum, and during atleast a part of the period for variation of the degree of vacuum,further covering the center of an opening of a crucible containing amelt of CsI:Tl with a shutter, in the step of faulting the non-columnarsection 36. As described above, the melt state of CsI:Tl is varied asthe degree of vacuum is varied. While the melt state is unstable,deposition may be continuously performed, thereby imparting anon-uniform thickness distribution. At this time, when the center of theopening of the crucible corresponding to the central region 36A of thenon-columnar section 36 is covered with the shutter, crystals may behardly deposited in the central region 36A. As a result, the deviationin the thickness distribution in the central region 36A is reduced orthe thickness distribution becomes uniform.

FIG. 7 is a view illustrating a radiological image detection apparatusaccording to another exemplary embodiment of the present invention.Further, the same components as those in the above describedradiological image detection apparatus 1 will be denoted by the samereference numerals, and their description will be omitted or simplified.

In a radiological image detection apparatus 101 illustrated in FIG. 7, ascintillator 118 of a radiological image conversion panel 102 isdirectly formed on the surface of a sensor panel 3 provided with atwo-dimensional arrangement of photoelectric conversion elements 26.That is, as a support of the scintillator 118, the sensor panel 3 isused.

The scintillator 118 includes a columnar section 134 and a non-columnarsection 136, and on the surface of the sensor panel 3, the non-columnarsection 136 and the columnar section 134 are sequentially continuouslyformed to be stacked in layers. Since between the sensor panel 3 and thecolumnar section 134, the non-columnar section 136 is interposed, theadhesion of the scintillator 118 with the sensor panel 3 is improved,and thus the scintillator 118 is suppressed from being peeled off fromthe sensor panel 3. The non-columnar section 136 has a non-uniformthickness distribution, and thus the resistance against stress such as ashear force acted on a junction portion between the columnar section 134and the non-columnar section 136 is improved, thereby improving thestrength. The columnar section 134 and the non-columnar section 136 maybe formed on the surface of the sensor panel 3 by the above describedvapor deposition method.

Also, in the present radiological image detection apparatus 101, betweenthe columnar section 134 of the scintillator 118 and the two-dimensionalarrangement of the photoelectric conversion elements 26 of the sensorpanel 3, the non-columnar section 136 of the scintillator 118 isinterposed. In this case, there is a concern that the light reflectionin the non-columnar section 136 may suppress the fluorescence occurringin each of columnar crystals of the columnar section 134 from beingincident on the corresponding photoelectric conversion element 26.Accordingly, the thickness of the non-columnar section 136 is preferablysmall within a range allowing the adhesion with the sensor panel 3 to besecured.

Each of the above described radiological image detection apparatus maydetect a radiological image with a high sensitivity and a highdefinition, and thus may be used while embedded within various devicesrequiring detection of a sharp image at a low radiation irradiationdose, including an X-ray imaging device for medical diagnosis such asmammography. For example, the device has a wide application rangethereof because it may be used as an X-ray imaging device for industrialuse for a non-destructive test, or as a device for detecting corpuscularbeams (α rays, β-rays, γ rays) besides electromagnetic waves.

Hereinafter, materials that may be used for respective componentsconstituting the sensor panel 3 will be described.

[Photoelectric Conversion Element]

Although inorganic semiconductor materials such as amorphous silicon areoften used as the photoconductive layers 20 of the aforementionedphotoelectric conversion elements 26 (refer to FIG. 1), any OPC (OrganicPhotoelectric Conversion) material disclosed in JP-A-2009-32854 can beused. A film formed out of the OPC material (hereinafter referred to asOPC film) can be used as the photoconductive layers 20. The OPC filmcontains an organic photoelectric conversion material, which absorbslight emitted from the scintillator and generates electric chargescorresponding to the absorbed light. Thus, the OPC film containing theorganic photoelectric conversion material has a sharp absorptionspectrum in a visible light range. Electromagnetic waves other than thelight emitted by the scintillator are hardly absorbed by the OPC film.Thus, noise generated by radioactive rays such as X-rays absorbed by theOPC film can be suppressed effectively.

It is preferable that the absorption peak wavelength of the organicphotoelectric conversion material forming the OPC film is closer to thepeak wavelength of light emitted by the scintillator in order to moreefficiently absorb the light emitted by the scintillator. Ideally, theabsorption peak wavelength of the organic photoelectric conversionmaterial agrees with the peak wavelength of the light emitted by thescintillator. However, if the difference between the absorption peakwavelength of the organic photoelectric conversion material and the peakwavelength of the light emitted by the scintillator is small, the lightemitted by the scintillator can be absorbed satisfactorily.Specifically, the difference between the absorption peak wavelength ofthe organic photoelectric conversion material and the peak wavelength ofthe light emitted by the scintillator in response to radioactive rays ispreferably not larger than 10 nm, more preferably not larger than 5 nm.

Examples of the organic photoelectric conversion material that cansatisfy such conditions include arylidene-based organic compounds,quinacridone-based organic compounds, and phthalocyanine-based organiccompounds. For example, the absorption peak wavelength of quinacridonein a visible light range is 560 nm. Therefore, when quinacridone is usedas the organic photoelectric conversion material and CsI(Tl) is used asthe scintillator material, the aforementioned difference in peakwavelength can be set within 5 nm so that the amount of electric chargesgenerated in the OPC film can be increased substantially to the maximum.

At least a part of an organic layer provided between the bias electrode22 and the charge collection electrode 24 can be formed out of an OPCfilm. More specifically, the organic layer can be formed out of a stackor a mixture of a portion for absorbing electromagnetic waves, aphotoelectric conversion portion, an electron transport portion, anelectron hole transport portion, an electron blocking portion, anelectron hole blocking portion, a crystallization prevention portion,electrodes, interlayer contact improvement portions, etc.

Preferably the organic layer contains an organic p-type compound or anorganic n-type compound. An organic p-type semiconductor (compound) is adonor-type organic semiconductor (compound) as chiefly represented by anelectron hole transport organic compound, meaning an organic compoundhaving characteristic to easily donate electrons. More in detail, of twoorganic materials used in contact with each other, one with lowerionization potential is called the donor-type organic compound.Therefore, any organic compound may be used as the donor-type organiccompound as long as the organic compound having characteristic to donateelectrons. Examples of the donor-type organic compound that can be usedinclude a triarylamine compound, a benzidine compound, a pyrazolinecompound, a styrylamine compound, a hydrazone compound, atriphenylmethane compound, a carbazole compound, a polysilane compound,a thiophene compound, a phthalocyanine compound, a cyanine compound, amerocyanine compound, an oxonol compound, a polyamine compound, anindole compound, a pyrrole compound, a pyrazole compound, a polyarylenecompound, a fused aromatic carbocyclic compound (naphthalene derivative,anthracene derivative, phenanthrene derivative, tetracene derivative,pyrene derivative, perylene derivative, fluoranthene derivative), ametal complex having a nitrogen-containing heterocyclic compound as aligand, etc. The donor-type organic semiconductor is not limited theretobut any organic compound having lower ionization potential than theorganic compound used as an n-type (acceptor-type) compound may be usedas the donor-type organic semiconductor.

The n-type organic semiconductor (compound) is an acceptor-type organicsemiconductor (compound) as chiefly represented by an electron transportorganic compound, meaning an organic compound having characteristic toeasily accept electrons. More specifically, when two organic compoundsare used in contact with each other, one of the two organic compoundswith higher electron affinity is the acceptor-type organic compound.Therefore, any organic compound may be used as the acceptor-type organiccompound as long as the organic compound having characteristic to acceptelectrons. Examples thereof include a fused aromatic carbocycliccompound (naphthalene derivative, anthracene derivative, phenanthrenederivative, tetracene derivative, pyrene derivative, perylenederivative, fluoranthene derivative), a 5- to 7-membered heterocycliccompound containing a nitrogen atom, an oxygen atom or a sulfur atom(e.g. pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline,quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline,pteridine, acridine, phenazine, phenanthroline, tetrazole, pyrazole,imidazole, thiazole, oxazole, indazole, benzimidazole, benzotriazole,benzoxazole, benzothiazole, carbazole, purine, triazolopyridazine,triazolopyrimidine, tetrazaindene, oxadiazole, imidazopyridine,pyralidine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine,tribenzazepine etc.), a polyarylene compound, a fluorene compound, acyclopentadiene compound, a silyl compound, and a metal complex having anitrogen-containing heterocyclic compound as a ligand. The acceptor-typeorganic semiconductor is not limited thereto. Any organic compound maybe used as the acceptor-type organic semiconductor as long as theorganic compound has higher electron affinity than the organic compoundused as the donor-type organic compound.

As for p-type organic dye or n-type organic dye, any known dye may beused. Preferred examples thereof include cyanine dyes, styryl dyes,hemicyanine dyes, merocyanine dyes (including zero-methine merocyanine(simple merocyanine)), trinuclear merocyanine dyes, tetranuclearmerocyanine dyes, rhodacyanine dyes, complex cyanine dyes, complexmerocyanine dyes, alopolar dyes, oxonol dyes, hemioxonol dyes,squarylium dyes, croconium dyes, azamethine dyes, coumarin dyes,arylidene dyes, anthraquinone dyes, triphenylmethane dyes, azo dyes,azomethine dyes, Spiro compounds, metallocene dyes, fluorenone dyes,flugide dyes, perylene dyes, phenazine dyes, phenothiazine dyes, quinonedyes, indigo dyes, diphenylmethane dyes, polyene dyes, acridine dyes,acridinone dyes, diphenylamine dyes, quinacridone dyes, quinophthalonedyes, phenoxazine dyes, phthaloperylene dyes, porphyrin dyes,chlorophyll dyes, phthalocyanine dyes, metal complex dyes, and fusedaromatic carbocyclic dyes (naphthalene derivative, anthracenederivative, phenanthrene derivative, tetracene derivative, pyrenederivative, perylene derivative, fluoranthene derivative).

A photoelectric conversion film (photosensitive layer) which has a layerof a p-type semiconductor and a layer of an n-type semiconductor betweena pair of electrodes and at least one of the p-type semiconductor andthe n-type semiconductor is an organic semiconductor and in which a bulkheterojunction structure layer including the p-type semiconductor andthe n-type semiconductor is provided as an intermediate layer betweenthose semiconductor layers may be used preferably. The bulkheterojunction structure layer included in the photoelectric conversionfilm can cover the defect that the carrier diffusion length of theorganic layer is short. Thus, the photoelectric conversion efficiencycan be improved. The bulk heterojunction structure has been described indetail in JP-A-2005-303266.

It is preferable that the photoelectric conversion film is thicker inview of absorption of light from the phosphor layer. The photoelectricconversion film is preferably not thinner than 30 nm and not thickerthan 300 nm, more preferably not thinner than 50 nm and not thicker than250 nm, particularly more preferably not thinner than 80 nm and notthicker than 200 nm in consideration of the ratio which does make anycontribution to separation of electric charges.

As for any other configuration about the aforementioned OPC film, forexample, refer to description in JP-A-2009-32854.

[Switching Element]

Although inorganic semiconductor materials such as amorphous silicon areoften used as an active layer of the switching elements 28, organicmaterials may be used, for example, as disclosed in JP-A-2009-212389.Organic TFT may have any type of structure but a field effect transistor(FET) structure is the most preferable. In the FET structure, a gateelectrode is provided partially an upper surface of an insulationsubstrate. An insulator layer is provided to cover the electrode andtouch the substrate in the other portion than the electrode. Further, asemiconductor active layer is provided on an upper surface of theinsulator layer, and a transparent source electrode and a transparentdrain electrode are disposed partially on the upper surface of thesemiconductor active layer and at a distance from each other. Thisconfiguration is called a top contact type device. A bottom contact typedevice in which a source electrode and a drain electrode are disposedunder a semiconductor active layer may be also used preferably. Inaddition, a vertical transistor structure in which a carrier flows inthe thickness direction of an organic semiconductor film may be used.

(Active Layer)

Organic semiconductor materials mentioned herein are organic materialsshowing properties as semiconductors. Examples of the organicsemiconductor materials include p-type organic semiconductor materials(or referred to as p-type materials simply or as electron hole transportmaterials) which conduct electron holes (holes) as carriers, and n-typeorganic semiconductor materials (or referred to as n-type materialssimply or as electrode transport materials) which conduct electrons ascarriers, similarly to a semiconductor formed out of an inorganicmaterial. Of the organic semiconductor materials, lots of p-typematerials generally show good properties. In addition, p-typetransistors are generally excellent in operating stability astransistors under the atmosphere. Here, description here will be made ona p-type organic semiconductor material.

One of properties of organic thin film transistors is a carrier mobility(also referred to as mobility simply) μ which indicates the mobility ofa carrier in an organic semiconductor layer. Although preferred mobilityvaries in accordance with applications, higher mobility is generallypreferred. The mobility is preferably not lower than 1.0×10⁻⁷ cm²/Vs,more preferably not lower than 1.0×10⁻⁶ cm²/Vs, further preferably notlower than 1.0×10⁻⁵ cm²/Vs. The mobility can be obtained by propertiesor TOF (Time Of Flight) measurement when the field effect transistor(FET) device is manufactured.

The p-type organic semiconductor material may be either a low molecularweight material or a high molecular weight material, but preferably alow molecular weight material. Lots of low molecular weight materialstypically show excellent properties due to easiness in high purificationbecause various refining processes such as sublimation refining,recrystallization, column chromatography, etc. can be applied thereto,or due to easiness in formation of a highly ordered crystal structurebecause the low molecular weight materials have a fixed molecularstructure. The molecular weight of the low molecular weight material ispreferably not lower than 100 and not higher than 5,000, more preferablynot lower than 150 and not higher than 3,000, further more preferablynot lower than 200 and not higher than 2,000.

As for such a p-type organic semiconductor material, a phthalocyaninecompound or a naphthalocyanine compound may be exemplarily used.Specific examples thereof are noted below. Also, M represents a metalatom, Bu represents a butyl group, Pr represents a propyl group, Etrepresents an ethyl group, and Ph represents a phenyl group.

Compound M R n R′ R″ 1 Si OSi(n-Bu)₃ 2 H H 2 Si OSi(i-Pr)₃ 2 H H 3 SiOSi(OEt)₃ 2 H H 4 Si OSiPh₃ 2 H H 5 Si O(n-C₈H₁₇) 2 H H 7 Ge OSi(n-Bu)₃2 H H 8 Sn OSi(n-Bu)₃ 2 H H 9 Al OSi(n-C₆H₁₃)₃ 1 H H 10 Ga OSi(n-C₆H₁₃)₃1 H H 11 Cu — — O(n-Bu) H 12 Ni — — O(n-Bu) H 13 Zn — — H t-Bu 14 V═O —— H t-Bu 15 H₂ — — H t-Bu 16 Si OSiEt₃ 2 — — 17 Ge OSiEt₃ 2 — — 18 SnOSiEt₃ 2 — — 19 Al OSiEt₃ 1 — — 20 Ga OSiEt₃ 1 — —

(Switching Element Constituent Components Other than the Active Layer)

There is no particular limitation in the material constituting the gateelectrode, the source electrode, or the drain electrode, as long as ithas a required conductivity. However, examples thereof may include atransparent conductive oxide such as ITO (indium-doped tin oxide), IZO(indium-doped zinc oxide), SnO₂, ATO (antimony-doped tin oxide), ZnO,AZO (aluminum-doped zinc oxide), GZO (gallium-doped zinc oxide), TiO₂,or FTO (fluorine-doped tin oxide), a transparent conductive polymer suchas PEDOT/PSS([poly(3,4-ethylenedioxythiophene)/polystyrene sulfonicacid), or a carbon material such as carbon nanotube. These electrodematerials may be film-formed by, for example, a vacuum evaporationmethod, a sputtering method, or a solution coating method.

There is no particular limitation in the material used for theinsulating layer, as long as it has a required insulating effect.Examples thereof may include an inorganic material such as silicondioxide, silicon nitride, or alumina, or an organic material such aspolyester (e.g., PEN (polyethylene naphthalate), PET (polyethyleneterephthalate)), polycarbonate, polyimide, polyamide, polyacrylate,epoxy resin, poly-para-xylylene resin, novolac resin, PVA (polyvinylalcohol), PS (polystyrene). These insulating film materials may befilm-formed by, for example, a vacuum evaporation method, a sputteringmethod, or a solution coating method.

Other configurations on the above described organic TFT may refer to thedescription of Japanese Patent Application Laid-Open No 2009-212389.

Also, in the active layer of the switching elements 28, for example, anamorphous oxide described in Japanese Patent Application Laid-Open No2010-186860 may be used. Hereinafter, an active layer containing theamorphous oxide included in a field effect transistor (FET) described inJapanese Patent Application Laid-Open No 2010-186860 will be described.The active layer serves as a channel layer of the FET, allowingelectrons or holes to move.

The active layer is configured to include an amorphous oxidesemiconductor. The amorphous oxide semiconductor may be film-formed at alow temperature, and thus may be appropriately formed on a flexiblesubstrate. The amorphous oxide semiconductor used in the active layermay be preferably an amorphous oxide that includes at least one kindelement selected from the group including In, Sn, Zn, and Cd, morepreferably an amorphous oxide that includes at least one kind selectedfrom the group including In, Sn, and Zn, and further more preferably, anamorphous oxide that includes at least one kind selected from the groupincluding In, and Zn.

Examples of the amorphous oxide used in the active layer, specifically,may include In₂O₃, ZnO, SnO₂, CdO, Indium-Zinc-Oxide (IZO),Indium-Tin-Oxide (ITO), Gallium-Zinc-Oxide (GZO), Indium-Gallium-Oxide(IGO), or Indium-Gallium-Zinc-Oxide (IGZO).

As for the film forming method of the active layer, a vapor-phase filmformation method may be preferably used with a polycrystalline sinteredbody of the oxide semiconductor as a target. Among vapor-phase filmformation methods, a sputtering method, or a pulsed laser depositionmethod (PLD method) is suitable. Further, from the view point of massproduction, the sputtering method is preferable. For example, the filmformation may be performed by an RF magnetron sputtering evaporationmethod while the degree of vacuum and the oxygen flow rate arecontrolled.

The film-formed active layer is determined to be an amorphous film,through a known X-ray diffraction method. The composition ratio of theactive layer may be obtained by an RBS (Rutherford Back Scattering)analysis method.

Further, the electrical conductivity of the active layer is preferably10⁻⁴ Scm⁻¹ or more and less than 10² Scm^(−I), and more preferably 10⁻¹Scm⁻¹ or more and less than 10² Scm⁻¹. A method of adjusting theelectrical conductivity of the active layer may include known methodssuch as an adjustment method according to oxygen defects, an adjustmentmethod according to a composition ratio, an adjustment method accordingto impurities, and an adjustment method according to an oxidesemiconductor material.

Other configurations on the above amorphous oxide may refer to thedescription of Japanese Patent Application Laid-Open No 2010-186860.

[Insulating Substrate]

The substrate is not limited particularly as long as it has requiredsmoothness. Examples of the substrate include glass, quartz, lighttransmissive plastic film, etc. Examples of the light transmissiveplastic film include films or the like, made from polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone(PES), polyether imide, polyetheretherketone, polyphenylene sulfide,polyalylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC),cellulose acetate propionate (CAP), etc. In addition, any organic orinorganic filler may be contained in these plastic films. It may beconsidered that aramid, bionanofiber, etc. having properties such asflexibility, low thermal expansion and high strength, which cannot beobtained in existing glass or plastic, are used preferably to form aflexible substrate.

(Aramid)

An aramid material has high heat resistance showing a glass transitiontemperature of 315° C., high rigidity showing a Young's modulus of 10GPa, and high dimensional stability showing a thermal expansioncoefficient of −3 to 5 ppm/° C. Therefore, when a film made from aramidis used, it is possible to easily form a high-quality film for asemiconductor layer, as compared with the case where a general resinfilm is used. In addition, due to the high heat resistance of the aramidmaterial, an electrode material can be cured at a high temperature tohave low resistance. Further, it is also possible to deal with automaticmounting with ICs, including a solder reflow step. Furthermore, sincethe aramid material has a thermal expansion coefficient close to that ofITO (indium tin oxide), a gas barrier film or a glass substrate, warpafter manufacturing is small. In addition, cracking hardly occurs. Here,it is preferable to use a halogen-free (in conformity with therequirements of JPCA-ES01-2003) aramid material containing no halogens,in view of reduction of environmental load.

The aramid film may be laminated with a glass substrate or a PETsubstrate, or may be pasted onto a housing of a device.

High intermolecular cohesion (hydrogen bonding force) of aramid leads tolow solubility to a solvent. When the problem of the low solubility issolved by molecular design, an aramid material easily formed into acolorless and transparent thin film can be used preferably. Due tomolecular design for controlling the order of monomer units and thesubstituent species and position on an aromatic ring, easy formationwith good solubility can be obtained with the molecular structure keptin a bar-like shape with high linearity leading to high rigidity ordimensional stability of the aramid material. Due to the moleculardesign, halogen-free can be also achieved.

In addition, an aramid material having an optimized characteristic in anin-plane direction of a film can be used preferably. Tensionalconditions are controlled in each step of solution casting, verticaldrawing and horizontal drawing in accordance with the strength of thearamid film which varies constantly during casting. Due to the controlof the tensional conditions, the in-plane characteristic of the aramidfilm which has a bar-like molecular structure with high linearityleading to easy occurrence of anisotropic physicality can be balanced.

Specifically, in the solution casting step, the drying rate of thesolvent is controlled to make the in-plane thickness-directionphysicality isotropic and optimize the strength of the film includingthe solvent and the peel strength from a casting drum. In the verticaldrawing step, the drawing conditions are controlled precisely inaccordance with the film strength varying constantly during drawing andthe residual amount of the solvent. In the horizontal drawing, thehorizontal drawing conditions are controlled in accordance with a changein film strength varying due to heating and controlled to relax theresidual stress of the film. By use of such an aramid material, theproblem that the aramid film after casting may be curled.

In each of the contrivance for the easiness of casting and thecontrivance for the balance of the film in-plane characteristic, thebar-like molecular structure with high linearity peculiar to aramid canbe kept to keep the thermal expansion coefficient low. When the drawingconditions during film formation are changed, the thermal expansioncoefficient can be reduced further.

(Bio-Nanofiber)

Components sufficiently small relative to the wavelength of lightproduce no scattering of the light. Accordingly, nanofibers may be usedas a support for a transparent flexible resin material. And, of thenanofibers, a composite material (occasionally referred to asbionanofiber) of bacterial cellulose and transparent resin can be usedpreferably. The bacterial cellulose is produced by bacteria (AcetobacterXylinum). The bacterial cellulose has a cellulose microfibril bundlewidth of 50 nm, which is about 1/10 as large as the wavelength ofvisible light. In addition, the bacterial cellulose is characterized byhigh strength, high elasticity and low thermal expansion.

When a bacterial cellulose sheet is impregnated with transparent resinsuch as acrylic resin or epoxy resin and hardened, transparentbionanofiber showing a light transmittance of about 90% in a wavelengthof 500 nm while having a high fiber ratio of about 60 to 70% can beobtained. By the bionanofiber, a thermal expansion coefficient (about 3to 7 ppm) as low as that of silicon crystal, strength (about 460 MPa) ashigh as that of steel, and high elasticity (about 30 GPa) can beobtained.

As for the configuration about the aforementioned bionanofiber, forexample, refer to description in JP-A-2008-34556.

[Flattening Layer and Adhesive Layer]

There is no specific limitation in the flattening layer 23 and theadhesive layer 25 as the resin layer which allows the scintillator 18and the photoelectric conversion elements 26 to be optically coupled, aslong as it may allow the fluorescence of the scintillator 18 to reachthe photoelectric conversion elements 26 without attenuation. As theflattening layer 23, a resin such as polyimide or parylene may be used,and polyimide with a good film-forming property is preferred. As for theadhesive layer 25, for example, a thermoplastic resin, a UV-curableadhesive, a heat curing adhesive, a room temperature setting adhesive, adouble-sided adhesive sheet may be used. However, from the viewpoint ofnot degrading the sharpness of an image, it is preferable to use anadhesive made of a low viscosity epoxy resin since it may form asufficiently thin adhesive layer with respect to an element size.

Hereinafter, specific examples of manufacturing the radiological imagedetection apparatus will be described, but the present invention is notlimited to these Manufacturing Examples.

Manufacturing Example 1

1. Manufacturing of a Radiological Image Conversion Panel

As the support 11, an alkali-free glass substrate for liquid crystals(0.7 mm thickness) was prepared. First, the support 11 wassurface-treated with Ar plasma so as to improve the adhesion with thescintillator. Then, the surface-treated support was set in a vacuumchamber for film formation of the scintillator. The vacuum chamber isprovided with a plurality of crucibles so as to independently heat eachof CsI and Tl of a raw material. After the chamber was exhausted, thedegree of vacuum of a device was set as 0.75 Pa by inflow of Ar in apredetermined amount. At the point of time when the melt state of theraw material was stabilized by heating the raw material crucible, thesupport was concentrically rotated by a device mechanism of the vacuumdevice. The shutter was opened to start the vapor deposition of thenon-columnar section 36.

Under this condition, film preparation was performed. At the point oftime when the thickness t2 of the non-columnar section 36 became 5 μm,the degree of vacuum was increased to 1 Pa to start the vapor depositionof the columnar section 34. When the degree of vacuum is varied, themelt state of the raw material is varied. Thus, before the vapordeposition was resumed, the shutter was closed. Then, when the meltstate was determined to be stabilized, the shutter was opened again. Atthe point of time when the thickness t1 of the columnar section 34became 500 μm, the heating of the raw material crucible was stopped.Through vapor deposition on the support by inhalation of the vacuumdevice, the scintillator 18 including the non-columnar section 36 andthe columnar section 34 was formed.

2. Test on Properties of Scintillator

2-1. Measurement on Thickness t2 of Non-Columnar Section and Thicknesst1 of Columnar Section

Any part of the scintillator 18 was fractured, and was observed in thegrowth direction of columnar crystals by SEM so as to measure the filmthicknesses of the columnar section 34 and the non-columnar section 36.As the film thickness value, an average value of values measured at 10locations randomly selected at the extracted part was used. Also, theSEM observation was performed after sputtering of Au to about 200 Åbecause CsI has non-conductivity.

2-2. Measurement of Crystal Diameter

A part of the scintillator 18 was peeled off from the support 11, andwas observed in the plane perpendicular to the growth direction of thecolumnar crystals by SEM so as to measure the columnar diameter(cross-sectional diameter of the columnar crystals). Observation wasperformed with a magnification (about 2,000×) that allows 100 to 200columnar crystals to be observed when the scintillator was viewed fromthe surface at one shot. Then, a value obtained by measuring and takingan average on the maximum values of the crystal diameters obtained forall the crystals included at the one shot is employed. Also, in a casewhere crystals are bonded to each other like in the non-columnar section36, a line connecting concave portions (recesses) occurring between theadjacent crystals was considered as a grain boundary between thecrystals, and the bonded crystals were separated to be the smallestpolygons so as to measure a crystal diameter. The crystal diameters (μm)were read to two decimal places, and the average value was determined byrounding off to one decimal place in accordance with JIS Z 8401.

When it is difficult to peel off the scintillator 18 from the support11, the scintillator 18 was vertically sliced in the growth direction ofthe columnar crystals at a position of about 100 μm from the support 11.Then etching of Ar ions was performed up to a distance allowing theinterfacial shape of CsI crystals attached on the support 11 to beobserved, and then observation was performed from the etching plane.Since CsI is non-conductive, SEM observation was performed aftersputtering Au to about 20 Å.

3. Manufacturing of Radiological Image Detection Apparatus

The sensor panel 3 was prepared, and on the surface thereof, a lowviscosity epoxy resin adhesive (manufactured by HUNTSMAN Corp, Araldite2020) diluted with a solvent was applied through spin-coating so thatthe thickness after solvent evaporation may be 15 μm. Then, the adhesivelayer 25 was formed. After the adhesive layer 25 formed on the sensorpanel 3 face the columnar section 34 side of the scintillator 18, theradiological image conversion panel 2 was bonded to the sensor panel 3via the adhesive layer 25 through heating.

Then, on a terminal unit of the sensor panel 3, a circuit board fordriving a TFT, and an integrated circuit IC for reading out electriccharges were adhered by an anisotropic conductive film, which wasconnected to a circuit board designed for control driving and ADconversion so as to provide the radiological image detection apparatusof Manufacturing Example 1.

Radiation was disposed to be incident from the sensor panel 3 side, anda radiological image was read out by controlling a PC for scanningconnected to the radiological image detection apparatus 1 via a cable.

Manufacturing Examples 2 to 6

Radiological image detection apparatus in Manufacturing Example 2 to 6were manufactured in the same manner as described in ManufacturingExample 1 except that the film thickness of the non-columnar section 36was adjusted as noted in Table 1 by changing the vapor deposition timeat the time of degree of vacuum of 0.75 Pa.

Manufacturing Examples 7 to 11

Radiological image detection apparatus in Manufacturing Example 7 to 11were manufactured in the same manner as described in ManufacturingExample 1 except that in the film formation of the non-columnar section36, the degree of vacuum was changed as noted in Table 1, and thecrystal diameter in the non-columnar section 36 was adjusted as noted inTable 1.

Manufacturing Example 12

As a support, in place of the glass substrate used in ManufacturingExample 1, a glass substrate which has a surface formed with anunevenness at a height of about 5 μm with 5 μm pitch through wet etchingwas used. Then, a radiological image detection apparatus inManufacturing Example 12 was manufactured in the same manner asdescribed in Manufacturing Example 1 except that in the formation of thescintillator 18, the columnar section was directly vapor-deposited onthe support without vapor deposition of the non-columnar section.

Manufacturing Example 13

The scintillator 18 was directly film-formed on the surface of thesensor panel 3 instead of the glass substrate used as a support inManufacturing Example 3 in the same condition of Manufacturing Example3. In the present embodiment, in the vicinity of the sensor panel 3, thenon-columnar section 36 is first formed, and then, the columnar section34 is formed, but bonding through a thermosetting adhesive is notperformed. Others than this processing were performed in the same manneras described in Manufacturing Example 3.

4. Test on Properties of Radiological Image Detection Apparatus

4-1. Sensitivity

As radiation, X-rays were used. At the irradiation of the X-rays, thesensor panel 3 was driven by an electrical circuit so as to read outelectric charges generated in each of the photoelectric conversionelements 26 by scintillation light. Then, the quantity of the generatedelectric charges was calculated by AD conversion after amplificationthrough a electric charge amplifier.

The quantity of electric charges (noise of a detection system) read outat non-irradiation of the X-rays was previously measured, and a valueobtained by subtracting this quantity from the quantity of electriccharges generated at the irradiation of the X-rays was set assensitivity. The result is noted in Table 1. Also, this value isindicated by a relative value with respect to 100 of sensitivity inManufacturing Example 12.

4-2. MTF (Modulation Transfer Function)

In accordance with IEC standards, an edge image obtained byphotographing an MTF edge made of W (tungsten) was computed so as toobtain an MTF curve. The result is noted in Table 1. Also, as comparedto the value of 2 cycle/mm, this value is indicated by a relative valuewith respect to 100 of the value in Manufacturing Example 12.

4-3. Overall Determination

The product of the test results of the sensitivity and the MTF was usedas indicator so as to determine the performance of the radiologicalimage detection apparatus. The product of the sensitivity and the MTF ispreferably 120 or more because a difference in performance may besignificantly recognized in a sensory evaluation of an image.

TABLE 1 Phosphor Film Forming Method Phosphor Shape Degree of vacuumNon-columnar diameter Columnar diameter Film Evaluation result Non- FilmMean Film Mean thickness Overall columnar Columnar thickness crystalPorosity thickness columnar ratio Sensi- Determi- Support sectionsection t2 diameter (%) t1 diameter t2/t1 tivity MTF nationManufacturing Alkali- 0.75 Pa 1 Pa 5 3.3 9.0 500 7.6 0.01 120 100 120Example 1 free glass Manufacturing Alkali- 0.75 Pa 1 Pa 10 3.0 9.2 5007.2 0.02 121 100 121 Example 2 free glass Manufacturing Alkali- 0.75 Pa1 Pa 25 3.0 9.0 500 6.8 0.05 123 101 124 Example 3 free glassManufacturing Alkali- 0.75 Pa 1 Pa 50 3.1 9.1 500 7.2 0.10 122 100 122Example 4 free glass Manufacturing Alkali- 0.75 Pa 1 Pa 125 3.4 9.3 5007.1 0.25 120 100 120 Example 5 free glass Manufacturing Alkali- 0.75 Pa1 Pa 170 3.2 9.3 500 7.0 0.34 121 94 114 Example 6 free glassManufacturing Alkali-  0.1 Pa 1 Pa 25 11.2 4.0 500 6.8 0.05 111 91 101Example 7 free glass Manufacturing Alkali-  0.3 Pa 1 Pa 25 8.0 7.0 5007.0 0.05 117 99 116 Example 8 free glass Manufacturing Alkali-  0.5 Pa 1Pa 25 6.2 8.8 500 7.0 0.05 123 100 123 Example 9 free glassManufacturing Alkali-  1.5 Pa 1 Pa 25 1.5 9.4 500 7.2 0.05 122 100 122 Example 10 free glass Manufacturing Alkali-   3 Pa 1 Pa 25 0.5 9.3 5007.0 0.05 122 100 122  Example 11 free glass Manufacturing Patterning — 1Pa — — — 500 6.8 — 100 100 100  Example 12 substrate ManufacturingPhoto- 0.75 Pa 1 Pa 25 3.1 9.0 500 6.9 0.05 98 96 94  Example 13detector (TFT) substrate

As clearly noted in Table 1, it can be seen that as compared to theradiological image detection apparatus having the scintillator 18including only the columnar section 34 in Manufacturing Example 12, theradiological image detection apparatus in Manufacturing Examples 1 to 11have a higher sensitivity and also may suppress image deterioration suchas image blur so as to achieve a high sharpness of an obtained image.

Also, through Manufacturing Examples 1 to 11, it can be seen that whenthe ratio t2/t1 of the thickness t2 of the non-columnar section 36 tothe thickness t1 of the columnar section 34 is within a preferred range,and the crystal diameter of the non-columnar section 36 is within apreferred range, it is possible to especially achieve a goodsensitivity, and to suppress image blur.

As described above, the present description discloses a radiologicalimage conversion panel provided with a phosphor containing a fluorescentmaterial that emits fluorescence by radiation exposure, in which thephosphor comprises, a columnar section formed by a group of columnarcrystals which are obtained through columnar growth of crystals of afluorescent material, and a non-columnar section, the columnar sectionand the non-columnar section are integrally formed to overlap in acrystal growth direction of the columnar crystals, and a thickness ofthe non-columnar section along the crystal growth direction isnon-uniform in a region of at least a part of the non-columnar section.

And, in the radiological image conversion panel disclosed in the presentdescription, a difference between a maximum thickness and a minimumthickness in a central region of the non-columnar section is less than adifference between a maximum thickness and a minimum thickness in aperipheral region of the non-columnar section.

And, in the radiological image conversion panel disclosed in the presentdescription, a deviation in a thickness distribution in a central regionof the non-columnar section is less than a deviation in a thicknessdistribution in a peripheral region of the non-columnar section.

And, in the radiological image conversion panel disclosed in the presentdescription, the thickness of the non-columnar section is non-uniformonly in the peripheral region.

And, in the radiological image conversion panel disclosed in the presentdescription, the thickness of the non-columnar section is distributedwithin a range of 5 μm or more and 125 μm or less.

And, in the radiological image conversion panel disclosed in the presentdescription, the non-columnar section is formed while comprising a groupof spherical crystals obtained by growing crystals of the fluorescentmaterial in a substantial spherical shape, in which at least a part ofthe group of the spherical crystals is fused in an in-plane direction.

And, the present description discloses a method of manufacturing theaforementioned radiological image conversion panel, in which thenon-columnar section and the columnar section are formed in this orderon a support by depositing crystals of the fluorescent material on thesupport by a vapor deposition method, in which when the non-columnarsection is formed, the crystals of the fluorescent material aredeposited on the support by varying a degree of vacuum.

And, the present description discloses a radiological image detectionapparatus provided with the aforementioned radiological image conversionpanel, and a sensor panel which detects fluorescence generated from theradiological image conversion panel and converts the fluorescence intoan electrical signal.

And, in the radiological image detection apparatus disclosed in thepresent description, the radiological image conversion panel and thesensor panel are bonded to each other so that a surface of the columnarsection side of the phosphor faces the sensor panel.

And, the radiological image detection apparatus disclosed in the presentdescription has a radiation entrance surface at the sensor panel side.

And, the radiological image detection apparatus disclosed in the presentdescription has a radiation entrance surface at the radiological imageconversion panel side.

The present invention has been described in detail with reference tospecific exemplary embodiments. However, it is apparent to those skilledin the art that various changes and modification may be made withoutdeparting from the spirit and scope of the present invention. Thepresent application is based on Japanese Patent Application No.2010-291390 filed 27 Dec. 2010, and the contents thereof areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

The present invention may detect a radiological image with a highsensitivity and a high definition, and thus may be used while embeddedwithin various devices requiring detection of a sharp image at a lowradiation irradiation dose, including an X-ray imaging device formedical diagnosis such as mammography. For example, the device has awide application range because it may be used as an X-ray imaging devicefor industrial use for a non-destructive test, or as a device fordetecting corpuscular beams (α rays, β-rays, γ rays) besideselectromagnetic waves.

REFERENCE SIGNS LIST

-   1: radiological image detection apparatus-   2: radiological image conversion panel-   3: sensor panel-   11: support-   16: TFT substrate-   18: scintillator-   20: photoconductive layer-   22: electrode-   23: flattening layer-   24: electrode-   25: adhesive layer-   26: photoelectric conversion elements-   28; switching element-   30: gate lines-   32: signal line-   34: columnar section-   36: non-columnar section-   38: connection terminal

The invention claimed is:
 1. A radiological image detection apparatuscomprising: a radiological image conversion panel comprising a phosphorcontaining a fluorescent material that emits fluorescence by radiationexposure; and a sensor panel which detects fluorescence generated fromthe radiological image conversion panel and converts the fluorescenceinto an electrical signal, wherein the phosphor comprises a columnarsection formed by a group of columnar crystals which are obtainedthrough columnar growth of crystals of a fluorescent material, and anon-columnar section, the columnar section and the non-columnar sectionare integrally formed on the sensor panel to overlap in a crystal growthdirection of the columnar crystals so that the sensor panel, thenon-columnar section and the columnar section are provided in thisorder, a thickness of the non-columnar section along the crystal growthdirection is non-uniform in a region of at least a part of thenon-columnar section, a difference between a maximum thickness and aminimum thickness in a central region of the non-columnar section isless than a difference between a maximum thickness and a minimumthickness in a peripheral region of the non-columnar section, a diameterof each crystal constituting the non-columnar section is 0.5 μm or moreand 7.0 μm or less, the crystals of the non-columnar section irregularlyoverlap, and some crystals thereof are fused to each other in athickness direction or an in-plane direction, and the non-columnarsection includes a non-crystalline part.
 2. The radiological imagedetection apparatus of claim 1, wherein a deviation in a thicknessdistribution in a central region of the non-columnar section is lessthan a deviation in a thickness distribution in a peripheral region ofthe non-columnar section.
 3. The radiological image detection apparatusof claim 1, wherein the thickness of the non-columnar section isnon-uniform only in the peripheral region.
 4. The radiological imagedetection apparatus of claim 1, wherein the thickness of thenon-columnar section is distributed within a range of 5 μm or more and125 μm or less.
 5. The radiological image detection apparatus of claim1, which has a radiation entrance surface at the sensor panel side. 6.The radiological image detection apparatus of claim 1, which has aradiation entrance surface at the radiological image conversion panelside.
 7. A method of manufacturing the radiological image detectionapparatus of claim 1, wherein the non-columnar section and the columnarsection are formed in this order on the sensor panel by depositingcrystals of the fluorescent material on the sensor panel by a vapordeposition method with varying at least one condition of a degree ofvacuum and a temperature of the sensor panel, wherein when thenon-columnar section is formed, the crystals of the fluorescent materialare deposited on the sensor panel by varying a degree of vacuum.
 8. Theradiological image detection apparatus of claim 1, wherein t2/t1 is from0.01 to 0.25, where t1 represents a thickness of the columnar sectionand t2 represents a thickness of the non-columnar section.
 9. Aradiological image detection apparatus comprising: a radiological imageconversion panel comprising a phosphor containing a fluorescent materialthat emits fluorescence by radiation exposure; and a sensor panel whichdetects fluorescence generated from the radiological image conversionpanel and converts the fluorescence into an electrical signal, whereinthe phosphor comprises a columnar section formed by a group of columnarcrystals which are obtained through columnar growth of crystals of afluorescent material, and a non-columnar section, the columnar sectionand the non-columnar section are integrally formed on the sensor panelto overlap in a crystal growth direction of the columnar crystals sothat the sensor panel, the non-columnar section and the columnar sectionare provided in this order, a thickness of the non-columnar sectionalong the crystal growth direction is non-uniform in a region of atleast a part of the non-columnar section, a deviation in a thicknessdistribution in a central region of the non-columnar section is lessthan a deviation in a thickness distribution in a peripheral region ofthe non-columnar section, a diameter of each crystal constituting thenon-columnar section is 0.5 μm or more and 7.0 μm or less, the crystalsof the non-columnar section irregularly overlap, and some crystalsthereof are fused to each other in a thickness direction or an in-planedirection, and the non-columnar section includes a non-crystalline part.10. The radiological image detection apparatus of claim 9, wherein thethickness of the non-columnar section is distributed within a range of 5μm or more and 125 μm or less.
 11. The radiological image detectionapparatus of claim 9, which has a radiation entrance surface at thesensor panel side.
 12. The radiological image detection apparatus ofclaim 9, which has a radiation entrance surface at the radiologicalimage conversion panel side.
 13. A method of manufacturing theradiological image detection apparatus of claim 9, wherein thenon-columnar section and the columnar section are formed in this orderon the sensor panel by depositing crystals of the fluorescent materialon the sensor panel by a vapor deposition method with varying at leastone condition of a degree of vacuum and a temperature of the sensorpanel, wherein when the non-columnar section is formed, the crystals ofthe fluorescent material are deposited on the sensor panel by varying adegree of vacuum.
 14. The radiological image detection apparatus ofclaim 9, wherein t2/t1 is from 0.01 to 0.25, where t1 represents athickness of the columnar section and t2 represents a thickness of thenon-columnar section.